1. Field of the Invention
The present invention relates generally to a resist material and a method for forming a resist pattern with the resist material, and more particularly to a chemical amplifier resist and a method for forming a resist pattern with the chemical amplifier resist material.
2. Description of the Prior Art
An integration degree in a semiconductor integrated circuit has been heightened, a large scale integrated circuit (LSI) and a very large scale integrated circuit (VLSI) are put to practical use, a minimum pattern width in the integrated circuit is on the order of sub-microns, and the minimum pattern width has been moreover shortened.
When a micro-pattern is formed, a thin film or a substrate planned to be patterned is covered with a resist, the resist is selectively exposed to light to form a latent image of a desired pattern in the resist, the resist is developed, and a patterned resist is formed on the thin film or the substrate. Thereafter, the thin film or the substrate not covered with the patterned resist is dry-etched by using the patterned resist as a mask, and the resist pattern is removed. Therefore, the thin film on the substrate is formed in a desired pattern. This technique is called a lithography technique, and the lithography technique is necessary to make the LSI or VLSI.
In this case, ultraviolet light of a g line (a wave of 436 nm) or an i line (a wave of 365 nm) is used as the exposure light in the lithography technique. However, because the minimum pattern width has been moreover fined, light having a more shortened wavelength such as far ultraviolet light, vacuum ultraviolet light, an electron ray, an X ray has been used as the exposure light. In particular, the use of an excimer laser such as a KrF laser (a wave of 248 nm) or an ArF laser (a wave of 193 nm) as the exposure light has been recently paid attention, and the excimer laser is expected to be effective for the formation of the micro-pattern.
In this application, a word xe2x80x9cradiation rayxe2x80x9d denotes light emitted from one of various light sources such as ultraviolet light, far ultraviolet light, vacuum ultraviolet light, an electron ray, an X ray, one of various lasers or the like.
To form a micro-pattern on the order of sub-microns by using the exposure light ranging from the far ultraviolet light to the vacuum ultraviolet light of which a wavelength is shorter than that of the ultraviolet light currently used, it is required that transparency of a sensitive material for the exposure light having a specific wavelength is superior. Also, it is required that a material used as a resist has a superior dry-etching resistance.
As a resist material having the superior transparency and the superior dry-etching resistance, a radiation ray sensitive material characterized in that the material is a polymer or a copolymer of acrylic ester or xcex1-substitution acrylic ester (acrylate resin) having an adamantane structure in an ester portion is proposed by inventors of this application in a Published Unexamined Japanese Patent Application H4-39665 (1992).
Also, as another resist material having the superior transparency and the superior dry-etching resistance, a chemical amplifier radiation ray sensitive material characterized in that the material is a polymer or a copolymer of acrylic ester or xcex1-substitution acrylic ester (acrylate resin) having an norbornane structure in an ester portion is proposed by the inventors in a Published Unexamined Japanese Patent Application H5-257284 (1993).
In each of the above resist materials, about 50% alicyclic group unit is included in the resin resist to obtain the dry-etching resistance. However, there is a case that a type of layer planned to be etched moreover requires of the dry-etching resistance.
However, it is difficult to heighten the dry-etching resistance in cases where the above conventional resist having a structure of the acrylate resin is used.
An object of the present invention is to provide, with due consideration to the drawbacks of such a conventional resist material, a resist material having an etching resistance superior to that of a resist having a structure of the acrylate resin and a method for forming a resist pattern with the resist material.
In the present invention, a polymer or a copolymer comprising a skeletal structure composed of cyclic hydrocarbon and hydrocarbon and one or more alkali-soluble groups protected by one or more side chains (or one or more protective groups) is used as a resist material. This resist material is mixed with an acid generating agent in a solvent, and the resist material is set to a condition of a resist solution. Thereafter, the resist solution is coated on a thin film planned to be patterned, so that a resist film is formed on the thin film. Thereafter, the resist film is exposed to exposure light. Therefore, the resist film is partially irradiated with a radiation ray, and acid is generated in the acid generating agent which is included in portions of the resist film irradiated with the radiation ray.
Thereafter, the resist film is post-baked. Therefore, a chemical reaction performed while using the acid as catalyst is accelerated by the post baking, and the side chains are detached from the alkali-soluble groups by the chemical reaction. Thereafter, when the resist film is immersed into alkali-developing solution, the polymer or the copolymer composed of the cyclic hydrocarbon, the hydrocarbon and the alkali-soluble groups having no protecting side chain is dissolved in the alkali-developing solution. As a result, the portions of the resist film irradiated with the radiation ray is removed and the resist film having a particular pattern is formed on the thin film.
Thereafter, the thin film is etched while using the patterned resist film as a mask. In this case, because it is ascertained by an inventor""s experiment that an etching resistance of a resin having a cyclic hydrocarbon as its skeletal structure is superior to that of the acrylate resin, even though the patterned resist film is used as a mask in the etching process, there is no probability that the patterned resist film is over-etched or deformed.
Accordingly, in cases where the resist material according to the present invention is used according to the above resist pattern forming method, the thin film can be correctly patterned even though a minimum pattern width required for the thin film is moreover shortened. Therefore, the resist material and the resist pattern forming method are useful for the manufacturing a semiconductor apparatus such as a semiconductor integrated circuit or the like.